HIV-1 antigens with discrete conformational forms in the V1/V2 domain and methods of use thereof

ABSTRACT

The present invention relates to a novel composition of HIV-1 Env proteins that contain structurally and immunologically distinct VI/V2 domains. Methods of isolating such proteins, and methods of using such proteins as immunogens, therapeutic agents, vaccines, and test compounds for use in identifying a HIV antiviral are also provided.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a U.S. National Phase of International Application No. PCT/US2013/058433, filed on Sep. 6, 2013, which claims the benefit of U.S. Provisional Application Ser. No. 61/697,979, filed Sep. 7, 2012. The contents of the foregoing applications are incorporated herein by reference in their entirety.

GOVERNMENT INTERESTS

This invention was made with government support under grant numbers R01 AI-46383, R01 AI102718-01 and P01 AI-0888610 from the National Institutes of Health. The United States government has certain rights to this invention.

FIELD OF THE INVENTION

The present invention relates to a novel composition of recombinant HIV-1 Env proteins that contain structurally and immunologically distinct V1/V2 domains.

BACKGROUND OF THE INVENTION

Recent studies have shown a role for the V1/V2 domain of the HIV-1 ENV protein as a target in HIV-1 vaccines. A series of potent and broadly neutralizing monoclonal antibodies (MAbs) targeting a class of quaternary epitopes that were dependent on several positions in the V2 region were isolated in one study (Walker et al., 2009, Science 326:285-289; Moore et al., 2011, Journal of Virology 85:3128-3141). These antibodies react preferentially with native trimeric Env complexes. Further studies have shown that a small conserved sequence in the V2 domain interacted with α4β7 integrin, the mucosal homing receptor for activated T cells, and that this interaction strongly enhanced infection of those cells (Nawaz et al., 2011, PLoS Pathog 7:e1001301; Cicala et al., 2009, Proc Natl Acad Sci USA 106:20877-20882). A third finding came from the analysis of correlates of protection in the recently concluded RV144 vaccine trial conducted in Thailand, the first HIV vaccine trial that resulted in some protection against infection (Rerks-Ngarm et al., 2009, N Engl J Med 361:2209-2220). Protection in this trial was shown to correlate with an increased titer of antibodies that bound to a V1/V2 fusion protein, but not to any other factor analyzed, including avidity and titers of Env-specific IgG and IgA, viral neutralizing activity or levels of Env-specific CD4+ T cells (Haynes et al., 2012, The New England Journal of Medicine 366:1275-1286).

SUMMARY OF THE INVENTION

The present invention relates in part to isolated and purified polypeptides comprising the V1/V2 domain of a HIV envelope (Env) protein having a structural configuration of a “C” form, as at least shown in FIG. 6 and FIG. 7. As used herein, “HIV” is meant to represent either HIV-1 or HIV-2, and any and all subtypes thereof. Upon review of the specification, it will be understood that any such polypeptide is encompassed within the scope of invention which possesses the ability present and maintain the conformational integrity of the “C” form of the V1/V2 domain. It is disclosed herein that this “C” form presents one of several structural conformations based on an alternative form of disulfide bonding within this V1/V2 domain, which dramatically impacts the immunoreactivity of these proteins. To this end, an embodiment of the present invention further relates to a polypeptide which presents and maintains the conformational, antigenic, and immunoreactive integrity of the alternative “C” form of the V1/V2 domain, including but not limited to wherein the polypeptide is native gp120, or wherein the polypeptide native is gp140, or wherein the polypeptide is a recombinant form of gp120, or wherein the polypeptide is a recombinant form of gp140. Thus, another embodiment of the present invention further relates to such a polypeptide maintaining the structural integrity as discussed herein where the recombinant gp120-based form comprises a portion of the gp120 coding region, again, such that the antigenicity immunoreactivity of the V1/V2 structural configuration of the “C” form is maintained. A specific, but non-limiting embodiment of the present invention relates to such a presented polypeptide wherein the amino-terminal sequence represents a portion of MuLV gp70, including but not limited to a polypeptide presenting the “C” form which has the amino acid sequence as set forth in FIG. 14 (SEQ ID NO: 2). An additional embodiment of the present invention relates to nucleic acid molecules encoding a polypeptide with at least 90% amino acid sequence identity to a polypeptide which presents and maintains the conformational, antigenic, and immunoreactive integrity of the alternative “C” form of the V1/V2 domain, as well as related recombinant DNA molecules housing such a nucleic acid molecule, and any cell line transfected or transformed with any such recombinant DNA molecule.

The present invention also relates to isolated and purified polypeptides comprising the V1/V2 domain of a HIV envelope (Env) protein having a structural configuration of yet another form, identified herein as a “B” form, as at least shown in FIG. 6 and FIG. 7, or in the alternative, presented as both a “B” form and an “A” form (““B”/“A” form”). Again, upon review of the specification, it will be understood that any such polypeptide is encompassed within the scope of invention which possesses the ability to present and maintain the conformational integrity of the “B” form of the V1/V2 domain, or in the alternative a “B”/“A” combined form. Either form/forms as disclosed herein will again present one of several structural conformations based on an alternative form of disulfide bonding within this V1/V2 domain, dramatically impacting the immunoreactivity of these proteins. As disclosed immediately above in regard to the “C” forms, the present invention further relates to a polypeptide which presents and maintains the conformational, antigenic, and immunoreactive integrity of the alternative “B” form (or in the alternative a “B”/“A” combined form) of the V1/V2 domain, including but not limited to wherein the polypeptide is native gp120, native gp140, recombinant gp120, recombinant form gp140, a construction based upon a portion of the gp120 or gp 140 coding region, again, such that the antigenicity and immunoreactivity of the V1/V2 structural configuration of the “B” form (or in the alternative a “B”/“A” combined form) are maintained. An additional, but non-limiting embodiment of the present invention relates to such a presented polypeptide wherein the amino-terminal sequence represents a portion of MuLV gp70, including but not limited to a polypeptide presenting the “B” form (or a “B”/“A” combined form) which has the amino acid sequence as set forth in FIG. 14 (SEQ ID NO:2). An additional embodiment of the present invention relates to nucleic acid molecules encoding a polypeptide with at least 90% amino acid sequence identity to a polypeptide which presents and maintains the conformational, antigenic, and immunoreactive integrity of the alternative “B” form of the V1/V2 domain, or in the alternative a combined “B”/“A” form) as well as related recombinant DNA molecules housing such a nucleic acid molecule, and any cell line transfected or transformed with any such recombinant DNA molecule. It will be evident upon review of this specification that combinations of an “A” form, a “B” form and/or a “C” form are also contemplated herein as relating to the present invention.

The present invention also relates to utilizing the polypeptides of the present invention, including but not limited to polypeptides which maintain the conformational integrity disclosed herein as a “C” form, a “B” form and/or a combined “B/A” form in methods of treating a HIV positive subject which involves administering to such a subject a pharmaceutical composition comprising any such polypeptide disclosed herein, or combination thereof, with such a pharmaceutical composition optionally containing a pharmaceutically active carrier. It will be the goal of any such treatment to result in a reduction in the HIV viral load of a subject.

The present invention further relates to utilizing the polypeptides of the present invention, including but not limited to polypeptides which maintain the conformational integrity disclosed herein as a “C” form, a “B” form and/or a combined “B/A” form in methods of vaccinating a human subject against infection or progression of HIV which comprises administration of a pharmaceutical composition comprising any, or combination thereof, of such polypeptides disclosed herein, with the pharmaceutical composition optionally containing a pharmaceutically active carrier, wherein administration of the pharmaceutical composition results in generation of an immune response against HIV infection.

To this end, the present invention relates to any such methodology utilized to induce an enhanced immunological response against a HIV antigen in a mammalian host, wherein the mammalian host is inoculated with a polypeptide disclosed herein as a “C” form, a “B” form and/or a combined “B/A” form and, optionally, a pharmaceutically acceptable carrier. Thus, the present invention also relates to any such pharmaceutical composition which comprises an effective amount of such a polypeptide and, optionally, a pharmaceutically acceptable carrier.

Another embodiment relates to methods of identifying an HIV antiviral compound, which comprises the steps of: (a) combining component (i)—a test compound, component (ii)—a “C” form-specific antibody, or a “B” form-specific antibody and/or an antibody which specifically recognizes a combination of the “B” and “A” form, and component (iii)—a polypeptide of “C” form, a “B” form and/or a combined “B/A” form; (b) measuring the effect the test compound has on the affinity of component (ii) for component (iii) of step (a); and, (c) comparing the effect the test compound has on the affinity of component (ii) for component (iii) versus the affinity of component (ii) for component (iii) in the absence of the test compound. Such methods may utilize test compounds selected from the group consisting of a peptide, a protein, a non-proteinaceous organic or inorganic molecule, DNA and RNA.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1. Evidence of structural/immunological heterogeneity of the V1/V2 domain was seen for several rgp120s upon sequential radioimmunoprecipitations. (a) Analyses by sequential immunoprecipitations revealed that a substantial fraction (˜25%) of three rgp120s tested were non-reactive with 697D, directed against a conformational V2 epitope. (b) C108g is a mAb isolated from an HIV-infected chimp that recognizes a glycan-dependent V1/V2 epitope overlapping with the PG9/PG16 site and possesses potent neutralizing activity against a limited set of viruses. C108g also recognized only a fraction of BaL rgp120 containing the correctly-folded V2 domain.

FIG. 2. To facilitate the structural analysis of the native V1/V2 domain, this region of a primary clade B Env (CaseA2) sequence was expressed as a fusion protein, joined to an N-terminal fragment of the MuLV Env protein, gp70. This fusion protein system allowed the expression of the V1/V2 domain as a native glycosylated and disulfide-bonded protein. Antibody reactivity with this V1/V2 fusion protein was the only variable shown to have a significant inverse correlation with risk of infection in the Thailand RV144 vaccine.

FIG. 3. Separation of the V1/V2 domain from the gp70 domain by cleavage at a proteolytic site engineered between the two domains shows that these regions form distinct and independent folded domains.

FIG. 4. The deglycosylated gp70-V1/V2_(CaseA2) protein is resolved as a doublet by SDS-PAGE under non-reducing conditions, indicating distinct conformational forms.

FIG. 5. The two V1/V2 conformational forms possess distinct immunoreactivities with V1/V2-specific mAbs. Mabs isolated from infected humans and mice immunized with rgp120 all specifically recognize the V1/V2 lower band form. Mabs from rats immunized with V1/V2 fusion protein recognize upper band or both bands.

FIG. 6. Three V1/V2 conformers can exist, which differ in their disulfide bond patterns. Structure A was determined for the H XB2 strain of HIV gp120 by Leonard et al., 1990, J. Biol. Chem. 265:10373-10382.

FIG. 7. Homogeneous conformational forms of the V1/V2 fusion protein were isolated by immunoaffinity chromatography and analyzed by mass spectrometry. The two forms were fractionated by immunoaffinity on columns containing lower band-specific mab 238. The flow-through contained upper band forms, while the column eluate contained the lower band form. The upper band form contained peptides at mass of 1573 and 2634 predicted for the C form, while the lower band form contained the complex peptide with mass of 4206 characteristic of forms A and B.

FIG. 8. Analysis of alternate V1/V2 conformeric forms of the CaseA2 and BaL V1/V2 fusion proteins. For the CaseA2 protein, rat Mab K10A11 (directed against a site in the gp70 carrier domain) pulls down both forms, mouse Mab SC-258 recognizes only lower form and human Mab 8.22.2 (from immunized Xenomouse, which contained only human Ig genes) recognized predominantly upper band form. The two forms were also seen for BaL V1/V2 fusion protein, although they were nor resolved as well. Again, K10A11 recognized both bands, rat Mab 10/76b, directed against a linear V2 epitope, recognized both upper and lower band equally well, while chimp Mab C108g recognizes only the lower band form. The C108g epitope was not well-expressed in this protein, perhaps because of its glycan-dependence.

FIG. 9. Analysis of reactivity of human vaccine sera with conformers of the gp70-V1/V2_(CaseA2) protein.

FIG. 10. Titrations of HIV-1-positive human immune sera show different patterns against specific V1/V2 conformers.

FIG. 11. Alignment of V1/V2 region of sequences analyzed in FIG. 12. Indicated are plasmid numbers and corresponding names of Envs these sequences were obtained from. Sequences (SEQ ID NOs: 7-48) are divided to indicate different regions of the V1/V2 domain; the conserved flanking regions, the V1 hypervariable region, the semi-conserved V2 region, the V2 hypervariable region and the V2 flank. The sequences are arranged by decreasing size of the V1 hypervariable region, and this order is reflected in the gel shown in FIG. 12.

FIG. 12. Analysis of conformational heterogeneity in V1/V2 domain demonstrated by SDS-PAGE analysis of deglycosylated gp70-fusion proteins (+PngaseF, Non-Reduced). The plasmid number and sequence name are indicated above each sample. Samples are arranged according to the list in FIG. 11, according to size of the V1 hypervariable region. The CaseA2 sequence (p3020) is repeated in each gel to serve as a standard. Protein markers are also included as size standards. All samples were deglycosylated by treatment with PNGaseF before analysis. The data presented in this FIG. 12 represents gels run in unreduced form, while the bottom gels.

FIG. 13. Analysis of conformational heterogeneity in V1/V2 domain demonstrated by SDS-PAGE analysis of deglycosylated gp70-fusion proteins (+PngaseF, Reduced). See also, FIG. 12 legend. The data presented in this FIG. 13 represents the same samples analyzed as per FIG. 12, but after reduction of disulfide bonds by treatment with DTT.

FIG. 14. The CaseA2 gp70-V1/V2 sequence.

FIG. 15. The sequence of P565 plasmid.

DETAILED DESCRIPTION OF INVENTION

The present invention is based on the discovery that the V1/V2 domain of HIV Env-based antigens possesses conformational heterogeneity resulting from alternative disulfide bonding, which dramatically impacts the immunoreactivity of these proteins. In accordance with the present invention, the conformationally heterogenous antigens can be resolved to provide HIV Env antigens with homogeneous conformational forms of the V1/V2 domain.

HIV envelope (Env) glycoproteins, including for example gp120 and p140, are known in the art and contain five constant and five variable domains. The V1/V2 domain comprises about 90 amino acids, including four cysteine residues designated herein as C1, C2, C3, and C4, with C1 being the most N-terminal and C4 being the most C-terminal. (FIGS. 2 6, and 7). The HIV Env antigens with homogeneous conformational forms of the V1/V2 domain provided herein are designated Form A, Form B, and Form C. In Form A, there is a disulfide bond between C1 and C4, and a disulfide bond between C2 and C3. In Form B, there is a disulfide bond between C1 and C3, and a disulfide bond between C2 and C4. In Form C, there is a disulfide bond between C1 and C2, and a disulfide bond between C3 and C4.

Forms A, B and C are present in native and recombinant HIV Env glycoproteins, and can be isolated from one another in accordance with the present invention. In particular, the present invention provides a method for isolating HIV Env antigens with Form A, or Form B, or Form C of the V1/V2 domain from each other to provide HIV Env antigens with a homogeneous conformational form of the V1/V2 domain. In particular, the different forms in a native or recombinant composition of HIV Env proteins can be separated from one another by immunoprecipitation with antibodies that are specific for the different conformations. For example, human Mab 8.22.2 (He et al., 2002, J. Immunol. 169:595-605) is specific for Form C. One of skill in the art can identify antibodies that are specific for the different conformations, and can perform immunoprecipitation, including serial immunoprecipitation, by methods known in the art to separate the different conformations. These forms can be fractionated by immunoaffinity methods using monoclonal antibodies that are specific for one of the distinct forms. The homogeneous forms may be obtained either in the depleted fraction or by elution of bound molecules.

Accordingly, in another embodiment, the present invention provides a composition of structurally and immunologically distinct HIV-1 antigens in which V1/V2 domains possess alternate disulfide bond patterns, i.e. Form A. Form B, or Form C, or combinations thereof, as disclosed herein. The antigens include at least the V1/V2 domain, and optionally other domains of the Env protein or other fusion partners. These antigens may consist of fusion glycoproteins that express the isolated V1/V2 domains as well as native gp120 and gp140 proteins that have been fractionated so that they contain homogeneously folded V1/V2 domains.

The antigens of the present invention are useful as antigens in immunoassays to characterize the specificity of antibodies directed against the V1/V2 domain in infected or immunized people. Accordingly, the invention further provides compositions comprising the antigens of the invention for use in such assays.

The antigens of the present invention are also useful as protein therapeutic agents for inhibiting functions mediated by the V1/V2 domain, and as immunogens in HIV vaccines. Accordingly, the present invention further provides pharmaceutical compositions comprising the antigens of the invention.

Formulations of the compositions useful in certain embodiments such as polypeptides, polynucleotides, or antibodies may be prepared for storage by mixing the selected composition having the desired degree of purity with optional physiologically pharmaceutically-acceptable carriers, excipients, or stabilizers (Remington's Pharmaceutical Sciences, 18th edition, A. R. Gennaro, ed., Mack Publishing Company (1990)) in the form of a lyophilized cake or an aqueous solution. Acceptable carriers, excipients or stabilizers are nontoxic to recipients and are preferably inert at the dosages and concentrations employed, and include buffers such as phosphate, citrate, or other organic acids; antioxidants such as ascorbic acid; low molecular weight polypeptides; proteins, such as serum albumin, gelatin, or immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, arginine or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugar alcohols such as mannitol or sorbitol; salt-forming counterions such as sodium; and/or nonionic surfactants such as Tween, Pluronics or polyethylene glycol (PEG).

Compositions to be used for in vivo administration should be sterile. This is readily accomplished by filtration through sterile filtration membranes, prior to or following lyophilization and reconstitution. The composition for parenteral administration ordinarily will be stored in lyophilized form or in solution.

Therapeutic compositions generally are placed into a container having a sterile access port, for example, an intravenous solution bag or vial having a stopper pierceable by a hypodermic injection needle. The route of administration of the composition is in accord with known methods, e.g. oral, injection or infusion by intravenous, intraperitoneal, intracerebral, intramuscular, intraocular, intraarterial, or intralesional routes, or by sustained release systems or implantation device. Where desired, the compositions may be administered continuously by infusion, bolus injection or by implantation device.

An effective amount of the compositions to be employed therapeutically will depend, for example, upon the therapeutic objectives, the route of administration, and the condition of the patient. Accordingly, it may be necessary for the therapist to titer the dosage and modify the route of administration as required to obtain the optimal therapeutic effect. A typical daily dosage may range from about 1 g/kg to up to 100 mg/kg or more, depending on the factors mentioned above. Typically, a clinician will administer the composition until a dosage is reached that achieves the desired effect. The progress of this therapy is easily monitored by conventional assays designed to evaluate blood glucose levels or other particular conditions of interest in a particular subject.

Pharmaceutical compositions may be produced by admixing a pharmaceutically effective amount of protein with one or more suitable carriers or adjuvants such as water, mineral oil, polyethylene glycol, starch, talcum, lactose, thickeners, stabilizers, suspending agents, etc. Such compositions may be in the form of solutions, suspensions, tablets, capsules, creams, salves, ointments, or other conventional forms.

In certain embodiments, compounds are formulated with pharmaceutically acceptable diluents, adjuvants, excipients, or carriers. The phrase “pharmaceutically or pharmacologically acceptable” refers to molecular entities and compositions that do not produce adverse, allergic, or other untoward reactions when administered to an animal or a human, e.g., orally, topically, transdermally, parenterally, by inhalation spray, vaginally, rectally, or by intracranial injection. The term parenteral as used herein includes subcutaneous injections, intravenous, intramuscular, intracistemal injection, or infusion techniques. Administration by intravenous, intradermal, intramusclar, intramammary, intraperitoneal, intrathecal, retrobulbar, intrapulmonary injection and/or surgical implantation at a particular site is contemplated as well.) Generally, this will also entail preparing compositions that are essentially free of pyrogens, as well as other impurities that could be harmful to humans or animals. The term “pharmaceutically acceptable carrier” includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, liposomes, capsids, nanocapsules, microcapsules and the like. The use of such media and agents for pharmaceutically active substances is well known in the art.

The pharmaceutical forms suitable for injectable use include sterile aqueous solutions or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersions. The carrier can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, and liquid polyethylene glycol, and the like), suitable mixtures thereof, and vegetable oils. The proper fluidity can be maintained, for example, by the use of a coating, such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants. The prevention of the action of microorganisms can be brought about by various antibacterial an antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars or sodium chloride. Prolonged absorption of the injectable compositions can be brought about by the use in the compositions of agents delaying absorption, for example, aluminum monostearate and gelatin.

In certain embodiments, the present invention provides a method of treating a subject comprising administration of a composition. As used herein, the term “subject” is used to mean an animal, preferably a mammal, including a human. The terms “patient” and “subject” may be used interchangeably.

The therapeutic compositions may be administered by any route that delivers an effective dosage to the desired site of action, with acceptable (preferably minimal) side-effects. Numerous routes of administration of agents are known, for example, oral, rectal, transmucosal, or intestinal administration; parenteral delivery, including intramuscular, subcutaneous, intramedullary injections, as well as intrathecal, intraperitoneal, intranasal, cutaneous or intradermal injections; inhalation, and topical application.

Therapeutic dosing is achieved by monitoring therapeutic benefit and monitoring to avoid side-effects. Preferred dosage provides a maximum localized therapeutic benefit with minimum local or systemic side-effects. Suitable human dosage ranges for the polynucleotides or polypeptides can be extrapolated from these dosages or from similar studies in appropriate animal models. Dosages can then be adjusted as necessary by the clinician to provide maximal therapeutic benefit for human subjects.

When a therapeutically effective amount of a composition of the present invention is administered by e.g., intradermal, cutaneous or subcutaneous injection, the composition is preferably in the form of a pyrogen-free, parenterally acceptable aqueous solution. The preparation of such parenterally acceptable protein or polynucleotide solutions, having due regard to pH, isotonicity, stability, and the like, is within the skill in the art. A preferred composition should contain, in addition to protein or other active ingredient of the present invention, an isotonic vehicle such as Sodium Chloride Injection, Ringer's Injection, Dextrose Injection, Dextrose and Sodium Chloride Injection, Lactated Ringer's Injection, or other vehicle as known in the art. The composition of the present invention may also contain stabilizers, preservatives, buffers, antioxidants, or other additives known to those of skill in the art. The agents of the invention may be formulated in aqueous solutions, preferably in physiologically compatible buffers such as Hanks's solution, Ringer's solution, or physiological saline buffer. For transmucosal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are generally known in the art.

The compositions of the invention may be in the form of a complex of the protein(s) or other active ingredient of present invention along with protein or peptide antigens.

The composition may further contain other agents which either enhance the activity of the protein or other active ingredient or complement its activity or use in treatment. Such additional factors and/or agents may be included in the pharmaceutical composition to produce a synergistic effect with protein or other active ingredient, or to minimize side effects.

Techniques for formulation and administration of the therapeutic compositions of the instant application may be found in “Remington's Pharmaceutical Sciences,” Mack Publishing Co., Easton, Pa., latest edition. When applied to an individual active ingredient, administered alone, a therapeutically effective dose refers to that ingredient alone. When applied to a combination, a therapeutically effective dose refers to combined amounts of the active ingredients that result in the therapeutic effect, whether administered in combination, serially or simultaneously.

The antigens of the present invention are useful for identifying, for example by screening, and for generating antibodies or antigen-binding fragments thereof that are specific for antigens with homogeneous conformational forms of the V1/V2 domain.

Antibodies may take the form of any type of relevant antibody fragment, antibody binding portion, specific binding member, a non-protein synthetic mimic, or any other relevant terminology known in the art which refers to an entity which at least substantially retains the binding specificity/neutralization activity. Thus, the term “antibody” as used in any context within this specification is meant to include, but not be limited to, any specific binding member, immunoglobulin class and/or isotype (e.g., IgG₁, IgG₂, IgG₃, IgG₄, IgM, IgA, IgD, IgE and IgM); and biologically relevant fragment or specific binding member thereof, including but not limited to Fab, F(ab′)2, Fv, and scFv (single chain or related entity). Therefore, it is well known in the art, and is included as review only, that an “antibody” refers to a glycoprotein comprising at least two heavy (H) chains and two light (L) chains inter-connected by disulfide bonds, or an antigen binding portion thereof. A heavy chain is comprised of a heavy chain variable region (VH) and a heavy chain constant region (CH1, CH2 and CH3). A light chain is comprised of a light chain variable region (VL) and a light chain constant region (CL). The variable regions of both the heavy and light chains comprise framework regions (FWR) and complementarity determining regions (CDR). The four FWR regions are relatively conversed while CDR regions (CDR1, CDR2 and CDR3) represent hypervariable regions and are arranged from NH.sub.2 terminus to the COOH terminus as follows: FWR1, CDR1, FWR2, CDR2, FWR3, CDR3, FWR4. The variable regions of the heavy and light chains contain a binding domain that interacts with an antigen while, depending of the isotype, the constant region(s) may mediate the binding of the immunoglobulin to host tissues or factors. That said, also included in the working definition of “antibody” are chimeric antibodies, humanized antibodies, a recombinant antibody, as human antibodies generated from a transgenic non-human animal, as well as antibodies selected from libraries using enrichment technologies available to the artisan. Antibody fragments are obtained using techniques readily known and available to those of ordinary skill in the art, as reviewed below. Therefore, an “antibody” is any such entity or specific binding member, which specifically binds the conformational epitope of the of the V1/V2 domain, as described herein. Therefore, the term “antibody” describes an immunoglobulin, whether natural or partly or wholly synthetically produced; any polypeptide or protein having a binding domain which is, or is substantially homologous to, an antibody binding domain. These can be derived from natural sources, or they may be partly or wholly synthetically produced. Examples of antibodies are the immunoglobulin isotypes and their isotypic subclasses; fragments which comprise an antigen binding domain such as Fab, scFv, Fv, dAb, Fd and diabodies, as discussed without limitation, infra. It is known in the art that it is possible to manipulate monoclonal and other antibodies and use techniques of recombinant DNA technology to produce other antibodies or chimeric molecules which retain the specificity of the original antibody Such techniques may evolve introducing DNA encoding the immunoglobulin variable region, or the complementarity determining regions (CDRs), of an antibody to the constant regions, or constant regions plus framework regions, of a different immunoglobulin. A hybridoma or other cell producing an antibody may be subject to genetic mutation or other changes, which may or may not alter the binding specificity of antibodies produced. Antibodies can be modified in a number of ways, and the term “antibody” should be construed as covering any specific binding member or substance having a binding domain with the required specificity. Thus, this term covers antibody fragments, derivatives, functional equivalents and homologues of “antibody” including any polypeptide comprising an immunoglobulin binding domain, whether natural or wholly or partially synthetic. Such an entity may be a binding fragment encompassed within the term “antigen-binding portion” or “specific binding member” of an antibody including but not limited to (i) a Fab fragment, a monovalent fragment consisting of the VL, VH, CL and CH domains; (ii) a F(ab′)2 fragment, a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region; (iii) a Fd fragment consisting of the VH and CH domains; (iv) a Fv fragment consisting of the VL and VH domains of a single arm of an antibody (v) a dAb fragment, which comprises a VH domain; (vi) an isolated complementarity determining region (CDR); (vii) a ‘scAb’, an antibody fragment containing VH and VL as well as either CL or CH; and (viii) artificial antibodies based upon protein scaffolds, including but not limited to fibronectin type III polypeptide antibodies (e.g., see U.S. Pat. No. 6,703,199, issued to Koide on Mar. 9, 2004 and PCT International Application Publication No. WO 02/32925). Furthermore, although the two domains of the Fv fragment, VL and VH, are coded for by separate genes, they can be joined, using recombinant methods, by a synthetic linker that enables them to be made as a single protein chain in which the VL and VH regions pair to form monovalent molecules (known as single chain Fv (scFv)). In one embodiment, the invention provides a method for generating HIV-1 Env proteins with structurally homogeneous V1/V2 domains, and the use of such uniform structures as antigens, immunogens and therapeutic reagents.

Polyclonal or monoclonal antibodies for use in accordance with the present invention may be raised by known techniques. Monospecific murine (mouse) antibodies showing specificity to a conformational epitope of a target of choice may be purified from mammalian antisera containing antibodies reactive against this region, or may be prepared as monoclonal antibodies using the technique of Kohler and Milstein (1975, Nature 256: 495-497). Monospecific antibody as used herein is defined as a single antibody species or multiple antibody species with homogenous binding characteristics, such as the mouse monoclonal antibodies exemplified herein with the 13C3 series of monoclonal antibodies. Hybridoma cells are produced by mixing the splenic lymphocytes with an appropriate fusion partner, preferably myeloma cells, under conditions which will allow the formation of stable hybridomas. The splenic antibody producing cells and myeloma cells are fused, selected, and screened for antibody production. Hybridoma cells from antibody positive wells are cloned by a technique such as the soft agar technique of MacPherson (1973, Soft Agar Techniques, in Tissue Culture Methods and Applications, Kruse and Paterson, Eds, Academic Press). Monoclonal antibodies are produced in vivo by injecting respective hydridoma cells into pristine primed mice, collecting ascetic fluid after an interval of time, and prepared by techniques well known in the art.

Beyond species specific monoclonal antibodies described above, the antibodies of the present invention may also be in the form of a “chimeric antibody”, a monoclonal antibody constructed from the variable regions derived from say, the murine source, and constant regions derived from the intended host source (e.g., human; for a review, see Morrison and Oi, 1989, Advances in Immunology, 44: 65-92). For example, the variable light and heavy DNA sequences from the rodent (e.g., mouse) antibody may be cloned into a mammalian expression vector. These light and heavy “chimeric” expression vectors are cotransfected into a recipient cell line and selected and expanded by known techniques. This cell line may then be subjected to known cell culture techniques, resulting in production of both the light chain and heavy chain of a chimeric antibody. Such chimeric antibodies have historically been shown to have the antigen-binding capacity of the original rodent monoclonal while significantly reducing immunogenicity problems upon host administration.

A logical improvement to the chimeric antibody is the “humanized antibody,” which arguably reduces the chance of the patient mounting an immune response against a therapeutic antibody when compared to use of a chimeric or full murine monoclonal antibody The strategy of “humanizing” a murine Mab is based on replacing amino acid residues which differ from those in the human sequences by site directed mutagenesis of individual residues or by grafting of entire complementarity determining regions (Jones et al., 1986, Nature 321: 522-526). This technology is again now well known in the art and is represented by numerous strategies to improve on this technology; namely by implementing strategies including, but not limited to, “reshaping” (see Verhoeyen, et al., 1988, Science 239: 1534-1536), “hyperchimerization” (see Queen, et al., 1991, Proc. Natl. Acad. Sci. 88:2869-2873) or “veneering” (Mark, et al., 1994, Derivation of Therapeutically Active Humanized and Veneered anti-CD18 Antibodies Metcalf end Dalton, eds. Cellular Adhesion Molecular Definition to Therapeutic Potential. New York: Plenum Press, 291-312). These strategies all involve to some degree sequence comparison between rodent and human sequences to determine whether specific amino acid substitutions from a rodent to human consensus is appropriate. Whatever the variations, the central theme involved in generating a humanized antibody relies on CDR grafting, where these three antigen binding sites from both the light and heavy chain are effectively removed from the rodent expressing antibody clone and subcloned (or “grafted”) into an expression vector coding for the framework region of the human antibody. For example, utilizing the above techniques a humanized antibody may be expressed wherein the CDR1, CDR2, and CDR3 regions of the variable light chain are prepared, and the CDR1, CDR2, and CDR3 regions of the variable heavy chain are prepared. Therefore, a “humanized antibody” is effectively an antibody constructed with only murine CDRs (minus any additional improvements generated by incorporating one or more of the above mentioned strategies), with the remainder of the variable region and all of the constant region being derived from a human source.

The invention also encompasses nucleic acid molecules encoding the proteins of the invention. Nucleic acid molecules within the invention can be cDNA, genomic DNA, synthetic DNA, or RNA, and can be double-stranded or single-stranded (i.e., either a sense or an antisense strand). Fragments of these molecules, which are also considered within the scope of the invention, can be produced, for example, by the polymerase chain reaction (PCR) or generated by treatment with one or more restriction endonucleases. A ribonucleic acid (RNA) molecule can be produced by in vitro transcription.

As used herein, both “protein” and “polypeptide” mean any chain of amino acid residues, regardless of length or post-translational modification (e.g., glycosylation or phosphorylation). The polypeptide can be a naturally occurring, synthetic, or a recombinant molecule consisting of a hybrid with one portion, for example, encoding all or a portion of a V1/V2 domain, and a second portion being encoded by all or part of a second gene.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety.

EXAMPLES Example 1

Isolated V1/V2 Domain of HIV-1 Env Exists in at Least Two Structurally and Immunologically Distinct Forms

The native V1/V2 domain of a clade B sequence (CaseA2) was expressed by fusion to the C-terminus of a 273 amino acid sequence fragment of the MuLV gp70 domain. This fusion glycoprotein was characterized by SDS-PAGE under various conditions, by radioimmunoprecipitation experiments with a panel of mAbs directed against V1/V2-specific epitopes, and by MALDI-TOF analysis of immunologically fractionated forms.

The CaseA2 gp70-V1/V2 sequence is set forth in FIG. 14.

The sequence of P565 plasmid is set forth in FIG. 15.

Plasmid has 1 HindIII site at the KL site in the V2 region

(SEQ ID NO. 49) CAG AAA GAA TAT GCA CTT TTT TAT AAG CTT GAT ATA GTA CCA ATA GAT AAT (SEQ ID NO. 50) Q K E Y A L F Y K L D I V P I D N This can be mutated and a unique HindIII site can be inserted by silent mutations into the highly conserved KL site at the beginning of the V1 sequence

(SEQ ID NO. 51) CCC CCC GCT AGC GTA AAA TTA ACC CCA CTC (SEQ. ID NO. 52) P P A S V K L T P L (SEQ ID NO. 6) CCC CCC GCT AGC GTA A/Ag cTt ACC CCA CTC                     HindIII

The V1/V2 domain of a number of HIV-1 Envs was expressed in isolated form as a disulfide-bonded glycoprotein joined to the C-terminus to a 273 amino acid fragment of the Friend MuLV gp70 protein. The CaseA2 V1/V2 fusion protein was radiolabeled and immunoprecipitated with monoclonal antibodies (mAbs) directed against a target in the gp70 carrier domain by capture of the antibody Fc regions with PANSORBIN®, a commercial preparation of crosslinked Staph A. The immunoprecipitated proteins were removed from PANSORBIN® by boiling in the presence of 1% SDS, and analyzed by SDS-PAGE before and after removal of all of the attached N-linked carbohydrate substituents both in non-reduced form and after reduction of disulfide bonds with dithiothreitol (DTT). Under non-reducing conditions a closely-spaced doublet was resolved on 10% gels at the position expected for the deglycosylated protein. These two bands coalesced into a single band with slightly lower mobility than the doublet after reduction, indicating that the doublet represented different disulfide-bonded conformeric forms. Analysis of samples immunoprecipitated with a variety of mAbs directed against sites in the V1/V2 domain contained either the upper or lower band, indicating that these represented two antigenically distinct conformeric forms. Analysis of the structure of the immunofractionated forms by MALDI-TOF mass spectrometry confirmed that these possessed distinct disulfide-bonded structures and allowed the assignment of the structures represented by the upper and lower band form.

These results demonstrate that the isolated V1/V2 domain of HIV-1 Env exists in at least two structurally and immunologically distinct forms.

Example 2

Heterogeneous Forms of V1/V2 Domains are not Limited to the Case-A2 Sequences

The biochemical method described above (SDS-PAGE of deglycosylated gp70-V1/V2 proteins under non-reducing conditions) allowed good resolution of structurally distinct V1/V2 forms of the Case-A2 sequence. However, applying the similar method to the BaL sequence resulted in a smaller separation between the two bands, and a modified SF162 sequence gave two bands that were barely distinguishable. Furthermore, for several other gp70-V1/V2 fusion proteins (e.g., the ConC sequence, or the Th023 clade A/E sequence) only a single band was observed. However, sequential immunoprecipitation assays revealed the presence of distinct conformational forms, indicating that the diverse forms were present, but could not be separated by gel electrophoresis.

Example 3

Direct Binding Studies with Rgp120/Rgp140 Proteins and Functional Studies

Evidence was also obtained for immunological heterogeneity in recombinant and native gp120 and gp140 immunogens. Sequential immunoprecipitations with monoclonal antibodies specific for distinct conformation epitopes in V1/V2 showed that these antibodies recognized only a fraction of the molecules (FIG. 1). Native and recombinant gp120 and gp140 proteins were recognized by MAbs specific for either the upper band-specific or lower band-specific epitopes, indicating the presence of both structures in these antigens. Finally, evidence has been presented that MAbs reactive with either upper band-specific or lower band-specific epitopes neutralized viral infectivity, indicating that both forms were present in functional Env proteins and suggesting that both contribute to viral binding and/or entry.

Analyses by sequential immunoprecipitations revealed that a substantial fraction (˜25%) of three rgp120s tested were non-reactive with 697D, directed against a conformational V2 epitope. (FIG. 1A). C108g is a mAb isolated from an HIV-infected chimp that recognizes a glycan-dependent V1/V2 epitope overlapping with the PG9/PG16 site and possesses potent neutralizing activity against a limited set of viruses. C108g also recognized only a fraction of BaL rgp120 containing the correctly-folded V2 domain. (FIG. 1B).

To facilitate the structural analysis of the native V1/V2 domain, this region of a primary clade B Env (CaseA2) sequence was expressed as a fusion protein, joined to an N-terminal fragment of the MuLV Env protein, gp70 (FIG. 2). This fusion protein system allowed the expression of the V1/V2 domain as a native glycosylated and disulfide-bonded protein. Separation of the V1/V2 domain from the gp70 domain by cleavage at a proteolytic site engineered between the two domains showed that these regions form distinct and independent folded domains (FIG. 3). The deglycosylated gp70-V1/V2_(CaseA2) protein was resolved as a doublet by SDS-PAGE under non-reducing conditions, indicating distinct conformational forms (FIG. 4; see also FIG. 6 for three distinct and possible confirmations of the V1/V2 domain). The two V1/V2 conformational forms possess distinct immunoreactivities with V1V2-specific mAbs. Mabs isolated from infected humans and mice immunized with rgp120 all specifically recognize the V1/V2 lower band form. Mabs from rats immunized with V1/V2 fusion protein recognize upper band or both bands (FIG. 5).

Homogeneous conformational forms of the V1/V2 fusion protein were isolated by immunoaffinity chromatography and analyzed by mass spectrometry. The two forms were fractionated by immunoaffinity on columns containing lower band-specific mab 238. The flow-through contained upper band forms, while the column eluate contained the lower band form. The upper band form contained peptides at mass of 1573 and 2634 predicted for the C form, while the lower band form contained the complex peptide with mass of 4206 characteristic of forms A and B (FIG. 7).

Alternate V1/V2 conformeric forms of the CaseA2 and BaL V1/V2 fusion proteins were analyzed (FIG. 8). For the CaseA2 protein, rat Mab K10A11 (directed against a site in the gp70 carrier domain) pulled down both forms; mouse Mab SC-258 recognized only lower form; and human Mab 8.22.2 (from immunized Xenomouse, which contained only human Ig genes) recognized predominantly upper band form. The two forms were also seen for BaL V1/V2 fusion protein, although they were not resolved as well. Again, K10A11 recognized both bands, rat Mab 10/76b, directed against a linear V2 epitope, recognized both upper and lower band equally well, while chimp Mab C108g recognized only the lower band form. The C108g epitope was not well-expressed in this protein, perhaps because of its glycan-dependence.

FIG. 9 shows an analysis of reactivity of human vaccine sera with conformers of the gp70-V1/V2_(CaseA2) protein. Titrations of HIV-1-positive human immune sera show different patterns against specific V1/V2 conformers (FIG. 10).

The wide variety of various pg 120 V1/V2 sequence sequences exemplified herein are aligned in FIG. 11. The respective SEQ ID NO., plasmid number and corresponding names of Envs from which these sequences represent are provided within FIG. 11. The respective sequences are divided to indicate different regions of the V1/V2 domain; the conserved flanking regions, the V1 hypervariable region, the semi-conserved V2 region, the V2 hypervariable region and the V2 flank. It is also noted that these sequences are arranged by decreasing size of the V1 hypervariable region, and this order is reflected in the gels shown in both FIG. 12 ((+PngaseF, Non-Reduced)) and FIG. 13 ((+PngaseF, Reduced-DTT). FIGS. 12 and 13 show an analysis of the conformational heterogeneity in V1/V2 domain, as demonstrated by SDS-PAGE analysis of deglycosylated gp70-fusion proteins, in both non-reduced (FIG. 12) and reduced (FIG. 13) form. The plasmid number and sequence name are indicated above each sample in both FIG. 12 and FIG. 13. Samples are arranged according to the listing of FIG. 11, described above, as according to size of the V1 hypervariable region. The CaseA2 sequence (p3020) is repeated in each gel to serve as a standard. Protein markers are also included as size standards. All samples represented in both FIGS. 12 and 13 were deglycosylated by treatment with PNGaseF before analysis; again, with the gels of FIG. 12 being run in unreduced form and the gels of FIG. 13 representing gels showing samples analyzed after reduction of disulfide bonds by treatment with DTT. Many of the samples demonstrate multiple bands, similar in complexity to those seen for the CaseA2 protein. These bands coalesce to a single form after reduction (bottom gels). In general, samples with longer V1 hypervariable regions (left-hand gels) tend to display greated conformational diversity than samples with short V1 regions (right-hand gels).

INDUSTRIAL APPLICABILITY

The invention has applications in the treatment and diagnosis of HIV-1 virus infection disease. All publications cited in the specification, both patent publications and non-patent publications, are indicative of the level of skill of those skilled in the art to which this invention pertains. All these publications are herein fully incorporated by reference to the same extent as if each individual publication were specifically and individually indicated as being incorporated by reference.

Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the following claims. 

What is claimed is:
 1. An isolated and purified fusion polypeptide comprising an amino-terminal sequence directly linked to a V1/V2 domain of a HIV envelope protein having a structural configuration of a “C” form, a “B” form, or a “B”/“A” combined form and comprising amino acid residues 304-401 of SEQ ID NO:2.
 2. The polypeptide of claim 1 wherein the HIV envelope protein has the sequence of a native gp120.
 3. The polypeptide of claim 1 wherein the HIV envelope protein has the sequence of a native gp140.
 4. The polypeptide of claim 1 wherein the HIV envelope protein is recombinant gp120.
 5. The polypeptide of claim 1 wherein the HIV envelope protein is recombinant gp140.
 6. The polypeptide of claim 4 wherein recombinant gp120 comprises a portion of the gp120 coding region, such that the antigenicity of the V1/V2 structural configuration of the “C” form, a “B” form, or a “B”/“A” combined form is maintained.
 7. The polypeptide of claim 1, wherein the amino-terminal sequence represents a portion of MuLV gp70.
 8. The polypeptide of claim 7 having the amino acid sequence of SEQ ID NO:2.
 9. A method of inhibiting HIV replication in an HIV positive subject comprising administering to the subject a pharmaceutical composition comprising a polypeptide of claim 1, said pharmaceutical composition optionally containing a pharmaceutically active carrier, wherein administration of the pharmaceutical composition results in a reduction in HIV viral load.
 10. A method of inducing neutralization of HIV viral infection in a human subject against infection or progression of HIV which comprises administration of a pharmaceutical composition which comprises a polypeptide of claim 1, said pharmaceutical composition optionally containing a pharmaceutically active carrier, wherein administration of the pharmaceutical composition results in generation of an immune response against HIV infection.
 11. A pharmaceutical composition, comprising: (a) an effective amount of a polypeptide of claim 1; and, (b) optionally, a pharmaceutically acceptable carrier.
 12. A method for inducing an enhanced immunological response against a HIV antigen in a mammalian host, said method comprising inoculating the mammalian host with a polypeptide of claim
 1. 13. A method of identifying a HIV antiviral compound, comprising: (a) combining component (i)—a test compound, component (ii)—a “C” form-specific, “B” form-specific, or “B”/“A” combined form-specific antibody, and component (iii)—a polypeptide of claim 1; (b) measuring the effect the test compound has on the affinity of component (ii) for component (iii) of step (a); and, (c) comparing the effect the test compound has on the affinity of component (ii) for component (iii) versus the affinity of component (ii) for component (iii) in the absence of the test compound.
 14. The method of claim 13 wherein component (i) is selected from the group consisting of a peptide, a protein, a non-proteinaceous organic or inorganic molecule, DNA and RNA. 